JP2014533441A - Light modulator and illumination system of microlithography projection exposure apparatus - Google Patents

Abstract

The illumination system of the microlithographic projection exposure apparatus includes a light modulator (38), which includes a modulator substrate (70) and mirrors (42a, 42b) supported by the modulator substrate (70). 42c). In this case, at least some of the adjacent mirrors partially overlap. The optical modulator further includes a plurality of actuators (86, 88) supported on the modulator substrate and configured to individually tilt the mirrors (42a, 42b, 42c). [Selection] Figure 9

Description

  The present invention relates generally to light modulators that include mirror arrays, and more particularly to illumination systems for microlithographic projection exposure apparatus that include such light modulators.

  Microlithography (also referred to as photolithography or simply lithography) refers to a technique for manufacturing integrated circuits, liquid crystal displays, and other microstructured devices. The microlithographic process including an etching process is for patterning a feature on a laminated thin film formed on a substrate such as a wafer. For each layer at the time of manufacture, a photoresist, that is, a material having photosensitivity to light of a specific wavelength is applied on the wafer in advance. Next, the wafer coated with the photoresist is exposed to projection light through a mask using a projection exposure apparatus. In this case, the mask includes a circuit pattern to be imaged on the photoresist. After the exposure, the photoresist is developed to generate an image corresponding to the circuit pattern included in the mask. In the subsequent etching process, a circuit pattern is formed on the laminated thin film on the wafer. Finally, the photoresist is removed. If the above steps are repeated using different masks, a multilayer microstructured part is obtained.

  The projection exposure apparatus usually includes an illumination system, and the illumination system irradiates a field on a mask having, for example, a rectangular or curved slit. The exposure apparatus further includes a mask stage for aligning the mask, an objective lens (also referred to as (lens)) that forms an irradiation field on the mask on the photoresist, and a wafer coated with the photoresist. A wafer alignment stage for alignment.

  One of the essential purposes in the development of a projection exposure apparatus is to enable lithography to define structures with smaller dimensions on the wafer. The fine structure leads to a high integration density that has a positive effect on the performance of the microstructured parts produced using the exposure apparatus.

  Various approaches have been pursued in the past to achieve the objectives described above. In one of these approaches, the projection light used to image the circuit pattern on the photoresist is made shorter in wavelength. This takes advantage of the fact that the minimum feature size that can be defined by lithography is approximately proportional to the wavelength of the projection light. Therefore, manufacturers of devices according to this approach emphasize the use of projection light having a shorter wavelength. The shortest wavelengths currently in use are 248 nm, 193 nm and 157 nm and are thus in the deep ultraviolet (DUV) or vacuum ultraviolet (VUV) spectral range. In the next generation devices that are commercially available, it is assumed that projection light having a shorter wavelength of about 13.5 nm is used. The wavelength of 13.5 nm is in the extreme ultraviolet (EUV) spectral range. In the case of EUV devices, a mirror is provided instead of a lens because the lens absorbs almost all of the EUV light.

  Another approach is to improve the mask illuminance. Ideally, the illumination system of the projection exposure apparatus irradiates each point in the field on the mask with projection light having a well-defined spatial irradiance distribution and angular irradiance distribution. The term “angular irradiance distribution” in this case represents how the total light energy in the light flux that converges to a specific point on the mask is distributed in each direction of the light beam.

  The angular irradiance distribution of the projection light incident on the mask is usually adapted to the type of pattern to be imaged on the photoresist. For example, a feature with a relatively large size may require a different angle when compared to a feature with a small size. The most common angular irradiance distributions are referred to as normal illumination settings, annular illumination settings, dipole illumination settings and quadruple illumination settings. These terms relate to the irradiance distribution of the pupil plane in the illumination system. For example, in the case of annular illumination setting, only the annular area of the pupil surface is irradiated. As described above, the angle range of the angular irradiance distribution in the projection light is slight, and all light rays enter the mask while being inclined at a similar angle.

  In the prior art, various means are known for changing the angular irradiance distribution of the projection light in the mask plane to achieve the desired illumination setting. In order to obtain maximum flexibility in generating different angular irradiance distributions in the mask plane, it has been proposed to use a mirror array to determine the irradiance distribution in the pupil plane.

  In Patent Document 1 (European Patent Publication No. 1262836), the mirror array is realized as a microelectromechanical system (MEMS) including more than 1000 micromirrors. In this case, each mirror can be tilted about two orthogonal tilt axes. Therefore, radiation incident on such a mirror device can be reflected in almost any hemispherical direction. The condenser lens disposed between the mirror array and the pupil plane converts the reflection angle by the mirror so as to match the position in the pupil plane. With the illumination system described in Patent Document 1, the pupil plane can be irradiated in a plurality of spots, and each spot is associated with a specific and one mirror, and the pupil is tilted over the pupil plane. It can move freely.

  Patent Document 2 (US Patent Application Publication No. 2006/0087634), Patent Document 3 (US Patent No. 7061582) and Patent Document 4 (International Publication No. 2005/026843) use mirror arrays. Similar illumination systems are known.

  In one embodiment of Patent Document 1 described above, the condensing optical system includes a plurality of parabolic reflection surfaces, the projection light beam incident on the reflection surfaces is divided into a plurality of sub-beams, and the plurality of mirrors are separated. Reflect individually. This ensures that the projection light does not propagate through the gap formed between adjacent mirrors. This not only reduces light loss, but also ensures that sensitive electronic components and actuators located below the mirror are not heated or damaged by projection light propagating through the gap. However, such a condensing optical system increases the complexity and cost of the illumination system.

  Patent Document 5 (US Patent Application Publication No. 2006/0209386) describes a digital micromirror device (DMD). The device in this case is provided with an anti-reflective coating to reduce the effect of stray radiation on device performance. The anti-reflective coating is placed directly on the DMD CMOS substrate and is primarily reflective to visible light.

  Patent Document 6 (US Pat. No. 7,167,297) describes a micromirror array having a non-rectangular outer periphery to reduce optical diffraction.

European Patent Application No. 1262836 US Patent Application Publication No. 2006/0087634 U.S. Pat. International Publication No. 2005/026843 Pamphlet US Patent Application Publication No. 2006/0209386 U.S. Patent No. 7167297 US Patent Application Publication No. 2009/0115990 International Publication No. 2010/040506 Pamphlet

  It is an object of the present invention to provide an optical modulator that reduces the risk that sensitive electronic components located below each mirror in the mirror array will be significantly heated and / or damaged by light.

  It is a further object of the present invention to provide an illumination system for a microlithographic projection exposure apparatus comprising a mirror array. The illumination system of the present invention eliminates the need for a condensing optical system that separates the projection light into a plurality of sub-beams, while the sensitive electronic components arranged below each mirror in the mirror array are significantly heated and projected by the projection light. To avoid the risk of damage.

  This object is achieved according to the first aspect of the present invention. In other words, this object is achieved by an optical modulator comprising a modulator substrate and a mirror array supported on the modulator substrate. In this case, at least some of the adjacent mirrors partially overlap. The plurality of actuators are supported by the modulator substrate and configured to tilt each mirror individually.

  By arranging adjacent mirrors in an overlapping manner, the amount of light that can enter a gap formed between adjacent mirrors and enter an actuator or electronic component can be greatly reduced. Which mirrors of adjacent mirrors overlap each other depends particularly on the direction of light when entering the mirror array. In this way, since the mirror itself shields sensitive components arranged below it from high-energy projection light, it is not necessary to provide an additional light shield such as an absorbing element.

  According to the most advantageous configuration of the invention, the light modulator comprises illumination optics arranged between the light source and the mirror array, the illumination optics being at least one extending over at least some of the adjacent mirrors. Light is reflected towards the mirror array so that one light beam illuminates each mirror. However, the present invention may be applied to an optical system in which a plurality of individual sub-beams separated from each other are generated by a condensing optical system. In this case, by arranging the mirrors in an overlapping manner, stray light can be prevented from reaching sensitive components arranged on the modulator substrate of the mirror array.

  Each mirror can overlap so that no light can enter through the gap formed between adjacent mirrors and therefore cannot enter one of the actuators or the electronic component.

  If at least some of the mirrors overlap, each mirror typically needs to be placed at a different height on the modulator substrate. In this case, the mirror height and lateral distance must be determined so that the gap between adjacent mirrors is placed in the shadow caused by the higher mirror.

  If the mirror array is a three-dimensional array, each mirror typically needs to be placed at three or more different heights on the modulator substrate.

  If each mirror is arranged at a different height, the array can have an absorptive coating placed on the underside of the substrate (76) in one of the mirrors facing the modulator substrate. Such an absorptive coating absorbs light reflected from a lower arrangement mirror toward a higher arrangement mirror.

  According to another aspect of the invention, the above-mentioned objects are achieved by an illumination system of a microlithographic projection exposure apparatus comprising a light source configured to generate projection light having a wavelength greater than 150 nm. The illumination system further includes a modulator substrate and a plurality of mirrors supported by the modulator substrate and arranged in an array such that a gap allowing gas to flow in and out remains between adjacent mirrors. Includes light modulator. The light modulator further includes a plurality of actuators supported on the modulator substrate and configured to individually tilt the mirror about the tilt axis. The optical modulator is provided with a plurality of absorption elements, each having an absorption surface for the projection light. Further, each absorbing element is disposed between adjacent mirrors to at least partially avoid projection light propagating through the gap from entering an actuator or electronic component supported on the modulator substrate. According to this aspect of the invention, the absorbing element is attached to a ridge extending at each mirror or gap. The illumination system further includes an illumination optical system disposed between the light source and the light modulator, the illumination optical system illuminating the light modulator with at least one light beam extending over at least two of the adjacent mirrors. The projection light is reflected toward the mirror array.

  The absorbing surface described above can be configured to absorb at least 99% of incident projection light.

  In other embodiments, the absorbing element is attached to the edge of the mirror. In this case, the absorption element can have an angled cross section.

  If the absorber element is attached to a post or ridge that extends in a gap, each mirror can also be suspended from these poles or ridges.

  It is a further object of the present invention to provide an optical modulator that reduces stray light during operation.

  According to the present invention, this object includes a modulator substrate, a mirror array, and a plurality of actuators supported on the modulator substrate and configured to individually tilt the mirror about two tilt axes. This is achieved by an optical modulator. In this case, the outer peripheral shape of some of the mirrors is obtained by rotating the basic shape at different angles around an axis at least approximately perpendicular to the tilt axis.

  Obtaining the outer peripheral shape described above contributes to avoiding a perfectly regular arrangement and thus avoiding stray light due to diffraction.

  This effect is further improved if the rotation angle is distributed almost randomly within a rotation angle range of, for example, 0.1 ° to 30 °, preferably 1 ° to 5 °.

Definitions The term “light” means all electromagnetic waves, in particular visible light, UV, DUV, VUV and EUV and X-rays.

  The term “light beam” in this specification means light whose propagation path can be represented by a straight line.

  As used herein, the term “beam” means a plurality of rays having a common source in the field plane.

  As used herein, the term “light beam” means light that passes through a particular lens or other optical element.

  As used herein, the term “optical raster element” refers to any optical element, such as a lens, prism, or diffractive optical element, arranged with other optical raster elements so that multiple optical channels are created and maintained. Means an optical element.

  As used herein, the term “integrator optical system” refers to an optical system that increases the product of NA · a, where NA is the numerical aperture and a is the illumination field region.

  As used herein, the term “condenser” refers to an optical element or system that establishes (at least approximately) a Fourier relationship between two planes, such as between the field plane and the pupil plane.

  The term “surface (surface)” in this specification means an arbitrary plane or curved surface in a three-dimensional space. In this case, the surface (plane) may be part of the object or may be completely separated from the object, as is common with the field or pupil plane.

  Various features and advantages of the present invention can be more readily understood from the following detailed description taken in conjunction with the accompanying drawings.

It is a schematic perspective view which shows a projection exposure apparatus. It is meridional sectional drawing which shows the illumination system which is a part of apparatus of FIG. It is a perspective view which shows the mirror array which the illumination system of FIG. 2 contains. It is a perspective view which shows the integrator optical system which the illumination system of FIG. 2 contains. It is sectional drawing which shows the mirror array which the illumination system of FIG. 2 contains according to 1st Embodiment which has an absorption element arrange | positioned on the board | substrate of this mirror array. FIG. 3 is a cross-sectional view of a mirror array included in the illumination system of FIG. 2 according to a second embodiment having an absorption element attached to the edge of each mirror. FIG. 4 is a cross-sectional view of a mirror array included in the illumination system of FIG. 2 according to a third embodiment having an absorbing element attached to a ridge extending in a gap between adjacent mirrors. FIG. 5 is a cross-sectional view of a mirror array included in the illumination system of FIG. 2 according to a fourth embodiment, which differs from the embodiment of FIG. 3 in that each mirror is suspended from a raised portion. FIG. 6 is a cross-sectional view of a mirror array included in the illumination system of FIG. 2 according to a fifth embodiment in which some of the adjacent mirrors partially overlap. FIG. 10 is a top view showing the mirror array of FIG. 9. It is a top view which shows the mirror array containing the rotated mirror according to 6th Embodiment.

I. General Configuration of Projection Exposure Apparatus FIG. 1 is a perspective view showing a projection exposure apparatus 10 according to the present invention in a greatly simplified state. The apparatus 10 comprises an illumination system 12 that generates a projection light beam (not shown). In this case, the illumination system 12 irradiates the field 14 on the mask 16 including a pattern 18 formed by a plurality of fine features 19 (shown schematically in FIG. 1 with thin lines). In the illustrated embodiment, the illumination field 14 has an annular segment shape, but may have other shapes, such as a rectangle.

  The projection objective 20 images the pattern 18 in the irradiation field 14 on the photosensitive layer 22 supported by the substrate 24, for example, on the photoresist. The substrate 24, which can be formed of a silicon wafer, is placed on a wafer stage (not shown) so that the top surface of the photosensitive layer 22 is accurately located in the imaging plane of the projection objective lens 20. The mask 16 is positioned in the plane of the projection objective 20 by a mask stage (not shown). In this case, since the projection objective lens 20 has a lateral magnification β of | β | <1, a reduced image 18 ′ of the pattern 18 in the irradiation field 14 is projected onto the photosensitive layer 22.

  In the illustrated embodiment, due to the configuration of the projection objective 20, the irradiation field 14 needs to be shifted with respect to the optical axis OA of the projection objective 20. In other types of projection objectives, the illumination field 14 can be centered on the optical axis OA.

  The mask 16 and the substrate 24 at the time of projection move along a scanning direction corresponding to the Y direction in FIG. In this case, since the irradiation field 14 is scanned across the mask 16, a pattern area larger than the irradiation field 14 can be continuously imaged. The speed ratio between the substrate 24 and the mask 16 is equal to the lateral magnification β of the projection objective lens 20. When the image is inverted by the projection objective lens 20 (β <0), the mask 16 and the substrate 24 move in the opposite directions as indicated by arrows A1 and A2 in FIG. However, the present invention can also be used in a stepper apparatus in which the mask 16 and the substrate 24 do not move during projection of the mask.

II. General Configuration of Illumination System FIG. 2 is a meridional sectional view showing the illumination system 12 of FIG. The figure is greatly simplified from the standpoint of clarity and does not reflect the actual size. This means in particular that different optical units are represented only by one or a small number of optical elements. In practice, these units can include much more lenses and other optical elements.

  The illumination system 12 includes a housing 29 and a light source 30 realized as an excimer laser in the illustrated embodiment. In this case, the light source 30 emits projection light having a wavelength of about 193 nm. Other types of light sources 30 and other wavelengths such as 248 nm or 157 nm can also be envisaged.

  In the illustrated embodiment, the light beam emitted from the light source 30 is incident on a beam expansion unit 32 that expands the light beam. In order to expand the light beam, the beam expanding unit 32 can comprise, for example, a plurality of lenses or a plane mirror. The expanded light beam 34 emitted from the beam expanding unit 32 hardly diverges. That is, they are almost parallel.

  The array of expanded light beams 34 emitted from the beam expanding unit 32 enters a light modulator 38 for generating a variable spatial irradiance distribution in the subsequent pupil plane. To that end, the light modulator 38 includes an array 40 of micromirrors 42 that can be individually tilted about two orthogonal axes by an actuator. The actuator is controlled by a control unit 43 connected to the overall system controller 45.

  FIG. 3 is a perspective view showing the array 40. This figure shows a state in which the two light beams LR1 and LR2 are reflected in different directions according to the inclination angle of the micromirror 42 on which the light beam is incident. The array 40 of FIGS. 2 and 3 includes only a 6 × 6 number of micromirrors 42, but may actually include hundreds or even thousands of micromirrors 42.

  Referring again to FIG. 2, the light modulator 38 further includes a prism 46 having a first plane 48a and a second plane 48b that are inclined with respect to the optical axis OA of the illumination system 12. The light beam 34 is reflected by these inclined planes 48a and 48b by total internal reflection. The first plane 48a reflects the light beam 34 toward the micromirror 42 of the mirror array 40, and the second plane 48b reflects the individual light beam reflected by the micromirror 42 toward the exit surface 49 of the prism 46. To do. The first plane 48a reflects the light beam 34 toward the micromirror 42 of the mirror array 40, and the second plane 48b reflects the individual light beam reflected by the micromirror 42 toward the exit surface 49 of the prism 46. To do. As described above, the angular irradiance distribution of the reflected light beam, and hence the projection light emitted from the emission surface 49, can be changed by individually inclining the micromirrors 42 of the microarray 40. Further details regarding the optical modulator 38 are described, for example, in US Pat.

  The angular irradiance distribution generated by the light modulator 38 is converted into a spatial irradiance distribution by the first capacitor 50 that directs the incident light beam to the integrator optical system 52.

  As shown in the perspective view of FIG. 4, the integrator optical system 52 in the illustrated embodiment has two optical raster plates 54 a and 54 b, and these plates 54 a and 54 b are configured by cylindrical microlenses 56. And an array orthogonal to each other. In this case, the integrator optical system generates a plurality of secondary light sources in the subsequent pupil plane in the illumination system 12. The second capacitor 58 establishes a Fourier relationship between the pupil plane 56 and the field stop plane 60 on which the adjustable field stop 62 is arranged. The second condenser 58 superimposes the light beam emitted from the second light source in the field stop plane 60 so that the field stop plane 60 is irradiated very uniformly.

  The field stop plane 60 is imaged by the field stop objective lens 64 on the mask plane 66 on which the mask 16 is arranged by a mask stage (not shown). Thereby, the adjustable field stop 62 is also imaged on the mask plane 66 and defines at least the short side surface of the irradiation field 14 extending along the scanning direction Y.

  The irradiance distribution generated in front of the integrator optical system 52 determines the irradiance distribution in the pupil plane 56 and thus the angular irradiance distribution in the field stop plane 60 and in the mask plane 66. Thus, by carefully setting the micromirrors 42 of the mirror array 40 by the control unit 43, almost any angular irradiance distribution can be quickly generated in the mask plane 66. Furthermore, this allows the angular irradiance distribution in the mask plane 66 to be adapted to the pattern 18 included in the mask 16. This pattern 18 can be imaged more accurately on the photosensitive layer 22 by optimizing the angular irradiance distribution.

III. Mirror array configuration
In the following, various embodiments of the mirror array 40 will be described with reference to FIGS.

1. Absorbing Element FIG. 5 is a sectional view showing a part of the mirror array 40 according to the first embodiment. In this case, the mirror array 40 includes a substrate 70 that supports a plurality of electronic components 72 (not shown in detail, but shown only as a single circuit layer). The substrate 70 further supports a plurality of mirror units 74, each mirror unit 74 including one of the micromirrors 42 and electronic components functionally associated with the micromirrors 42. In addition, each micromirror 42 includes a mirror substrate 76 and a reflective coating 78 formed on the mirror substrate 76, for example, consisting of a plurality of thin layers having alternating refractive indices.

  Further, each mirror unit 74 includes a base 80 that supports two semiconductor connecting members 82 and 84. With these members 82 and 84, the micromirror 42 can be tilted around two orthogonal tilt axes defined by the configuration of the semiconductor connecting members 82 and 84. The mirror unit 74 also includes a plurality of actuators 86 and 88 configured to tilt the micromirror 42 associated with each mirror unit 74 about two orthogonal tilt axes. In order to enable tilting around the tilting axis, these actuators 86 and 88 can exert an electrostatic force as described in, for example, Patent Document 8 (WO 2010/040506 pamphlet).

  In the illustrated embodiment, the base 80 of the mirror unit 74 is mounted on the electronic component 72, but may be mounted directly on the substrate 70 as is well known in the art of the present invention.

  A gap 90 necessary to avoid contact when the micromirrors 42 are inclined by the actuators 86 and 88 remains between the adjacent micromirrors 42 in the mirror array 40. These gaps 90 also have the advantage of allowing gas to flow in and out of cavities formed below the micromirrors 42. The inflow and outflow of gas contributes to removing convection heat generated by the electronic component 72 and the projection light 34 being absorbed by the reflective coating 78 of the micromirror 42.

  However, since the projection light 34 is incident on the mirror array 40 as a single and continuous projection light beam, not only the gas but also a part of the projection light 34 can pass through the gap 90. In the illustrated embodiment, a portion of projection light 34 is indicated by arrow 92. If a portion 92 of the projection light 34 enters the actuators 86, 88 and / or the electronic component 72, it will be absorbed by these components, resulting in a temperature rise that can impair the operation of the mirror array 40. Furthermore, high energy projection light may partially ionize actuators 86, 88 and / or 88 by transferring a portion of the energy to scattered electrons (Compton effect). In addition, the effects of high energy projection light can cause material degradation in the long run.

  In order to avoid at least some of the adverse effects that may be caused by the projection light incident on the actuators 86, 88 and / or the electronic component 72, a plurality of absorbing elements 94 are disposed between the adjacent micromirrors. These absorbing elements 94 include an absorbing surface 96 that is configured to absorb most of the projected light propagating through a gap formed between adjacent micromirrors 42. In the illustrated embodiment, the absorbing element 94 is disposed on the electronic component 72. The absorbing element 94 can also be configured by only the absorbing surface 96, and in that case, the absorbing element 94 is directly disposed on the electronic component 72.

  FIG. 6 is a cross-sectional view showing a part of the mirror array 240 according to the second embodiment. The absorbing element 94 in the illustrated embodiment is not attached to the substrate 70, the actuators 86 and 88, or the electronic components supported by the substrate 70, but is attached to the edge 98 of the micromirror substrate 76. Since the absorption element 94 in this case has an angled cross section, the micromirror 42 can be freely tilted around the two tilt axes without contacting the adjacent micromirror together with the absorption element 94. The attachment of the absorption element 94 to the micromirror substrate 76 has the advantage that the projection light is completely prevented from entering the gap 90. Thereby, the heat generated by the projection light absorbed by the absorption element can be kept away from the sensitive electronic component 72 and the actuators 86 and 88, and the mirror flows by the gas flowing on the surface of the mirror array 240. It can be more easily removed from the array 240.

  In principle, the absorbing element 94 may support the reflecting surface instead of providing the absorbing surface (in this case, strictly speaking, it cannot be called an absorbing element). In this case, the reflection surface of the absorption element 94 reflects the projection light in the same direction as that on the surface of the micromirror 42 covered with the reflection coating 78.

  The mirror array 340 of the third embodiment shown in FIG. 7 includes an absorbing element 94 disposed on the raised portion 100 that stands upright between the micromirrors 42 on the substrate 70. The effect of the absorbing element 94 in this case is similar to the effect of the absorbing element 94 of the mirror array 240 shown in FIG.

  The fourth embodiment of the mirror array 440 shown in FIG. 8 is mainly that the micromirror 42 is not supported by the semiconductor connecting member and is hung from the raised portion 100 to which the absorbing element 94 is attached. This is different from the mirror array 340 shown in FIG. A bending strip 102 extends between the raised portion 100 and the edge 98 of the micromirror substrate 76 to suspend the absorber element 94 in the illustrated embodiment.

2. Mirror Overlap FIG. 9 is a cross-sectional view of a mirror array 540 according to the fifth embodiment. In this case, at least some of the adjacent micromirrors partially overlap. For this purpose, the micromirrors are arranged on the substrate 70 at different heights. More specifically, the first micromirror 42a is disposed at a smaller height on the substrate 70 than the second micromirror 42b. As shown in the cross-sectional view of FIG. 9, the first and second micromirrors 42a and 42b are alternately different in height along one direction.

  Since the projection light 34 is incident on the mirror array 540 with an inclination, it is not necessary to partially overlap all of the adjacent first and second micromirrors 42a and 42b. For example, the two micromirrors 42a and 42b shown in the center of FIG. 9 do not overlap. This is because, in this case, the projection light 34 cannot enter the gap 90 formed between the two micromirrors 42a and 42b, and therefore is incident on one of the actuators 86 and 88 or the electronic component 72. Because there is no.

  However, with respect to the other micromirrors 42a and 42b shown in FIG. 9, the projection light 34 can be reliably prevented from reaching the actuators 86 and 88 or the electronic component 72 only by arranging the micromirrors 42a and 42b in an overlapping manner. Is done. In other words, with respect to the other micromirrors 42a and 42b, the projection light 34 in the vicinity of the gap 90 is basically incident on the first micromirror 42a having a smaller height and then adjacent to the second second having a higher height. Reflected toward the lower side of the micromirror 42b. In order to avoid the projection light incident on the lower side of the second micro mirror 42b from being reflected toward the actuators 86, 88 or the electronic component 72, the lower side of the second micro mirror 42b is formed by an absorbent coating 106. It is covered.

  Basically, the micromirrors in a three-dimensional array need to be arranged on the substrate 70 at three different heights. Basically, micromirrors can be stacked along two orthogonal directions only when arranged at three different heights.

  This point is shown in the top view of FIG. In this case, the third micromirrors 42c are alternately arranged with the first and second micromirrors 42a and 42b. The third micromirror 42c has a maximum height on the substrate 70. Only the first micromirrors 42a arranged in the shadow of the micromirrors 42b or 42c having a larger height do not overlap with the micromirrors 42b and 42c having a larger height. The direction of the shadow depends on the incident direction of the projection light 34.

  Needless to say, the micromirrors 42a, 42b, and 42c are arranged so that all of the adjacent micromirrors overlap with each other, and therefore a completely regular arrangement by these micromirrors 42a to 42c can be realized. However, leaving a larger gap 90 between adjacent micromirrors is advantageous in removing convective heat.

  Further, various other arrangements of the actuators 86 and 88 are possible. For example, even when the micromirrors 42a to 42c are arranged at different heights on the substrate 70, the actuators 86 and 88 can all be arranged in the same plane. Furthermore, it can be assumed that the actuators 86 and 88 are directly attached to the lower portions of the micromirrors 42a to 42c.

  Although the embodiment described above relates to a VUV projection exposure apparatus, the present invention can be similarly applied to an EUV apparatus including a light source that generates projection light having a wavelength of less than 50 nm.

3. Rotation Arrangement FIG. 11 is a top view showing a mirror array 640 according to the sixth embodiment. The configuration of the mirror array 640 in this case is essentially the same as the configuration of the first embodiment shown in FIG. Each micromirror 42 in the illustrated embodiment can also be individually tilted around two tilt axes by actuators 86 and 88 (shown only in FIG. 5) supported by the modulator substrate 70. The outer peripheral shape of the micromirror 42 is obtained by rotating the basic shape (square in the illustrated embodiment) at different angles around the rotation axis RA at least substantially orthogonal to the tilt axis. The rotation axis RA in the illustrated embodiment extends so as to be orthogonal to the drawing.

  The point described above does not mean that the micromirror can be rotated around the rotation axis RA during the operation of the optical modulator. Such rotational degrees of freedom can be arbitrarily given, but are not essential. Here, the term “rotation” merely describes the structural arrangement of the mirror array 640 obtained by conceptually rotating the basic mirror by different rotation angles. In the illustrated embodiment, the rotation angle varies approximately randomly within a range of 1 ° to 5 °.

  This almost random arrangement significantly reduces the regularity of the mirror array 640, thereby reducing the amount of stray light due to diffraction.

As shown in the enlarged cutaway view of FIG. 11, when the edge 98 of the micromirror is worn out irregularly, the amount of stray light due to diffraction can be further reduced.

Claims (17)

An optical modulator (38),
a) a modulator substrate (70);
b) an array of mirrors (540) supported by the modulator substrate (70) and partially overlapping by at least some adjacent mirrors (42a, 42b, 42c);
c) a plurality of actuators (86, 88) supported by the modulator substrate (70) and configured to individually tilt the mirrors (42a, 42b, 42c);
Including light modulator.   The modulator according to claim 1, wherein the mirrors (42a, 42b, 42c) are arranged at different heights on the modulator substrate (70).   The modulator according to claim 2, wherein the mirrors (42a, 42b, 42c) are arranged at three or more different heights on the modulator substrate (70).   4. The modulator according to claim 1, wherein a lower side of the substrate (76) of one of the mirrors (42 a, 42 b, 42 c) faces the modulator substrate (70). And a modulator in which an absorbent coating (106) is disposed.   6. An optical system according to any one of claims 1 to 5, comprising a light source configured to generate light.   The optical system according to claim 5, wherein the light (34) generated by the light source cannot enter through a gap (90) formed between adjacent mirrors (42a, 42b, 42c), Therefore, the optical system on which the mirrors (42a, 42b, 42c) overlap so that they cannot enter one of the actuators (86, 88) supported on the modulator substrate (70) or the electronic component (72). The optical system according to claim 5 or 6,
a) at least one light arranged between the light source (30) and the array of mirrors (42a, 42b, 42c) and b) extending over several adjacent mirrors (42a, 42b, 42c) An optical system including an illumination optical system (46) that reflects the light (34) toward the array of mirrors such that a beam illuminates the array of mirrors.   The optical system according to any one of claims 5 to 7, wherein the optical system is an illumination system of a microlithography projection exposure apparatus. An optical modulator (38),
a) a modulator substrate (70);
b) an array of mirrors (42aa, 42ab, 42ac, 42ba, 42bb, 42ca);
c) a plurality of actuators (86, 88) supported by the modulator substrate (70) and configured to individually tilt the mirror about two tilt axes;
The outer peripheral shape of at least some of the mirrors (42) is an optical modulator obtained by rotating the basic shape at different angles around a rotation axis (RA) at least approximately perpendicular to the tilt axis.   10. The modulator according to claim 9, wherein the rotation angle is distributed almost randomly within a certain rotation angle range.   The modulator according to claim 10, wherein the range is 0.1 ° to 30 °.   12. A modulator as claimed in claim 11, wherein the range is between 1 [deg.] And 5 [deg.].   13. Modulator according to any one of claims 9 to 12, wherein at least some edges of the mirror are worn out irregularly. An optical modulator,
a) a modulator substrate (70);
b) A plurality of mirrors supported by the modulator substrate (70) and arranged in an array (240, 340, 440) such that a gap (90) through which gas can flow in and out is left between adjacent mirrors ( 42) and
c) a plurality of actuators (86, 88) supported by the modulator substrate (70) and configured to individually tilt the mirror (42) about a tilt axis;
d) The actuator having an absorption surface for light and disposed between the adjacent mirrors (42) so that the light propagating through the gap (90) is supported by the modulator substrate (70). (86, 88) or a plurality of absorbing elements (94) that at least partially avoid entering the electronic component;
Including light modulator.   15. The optical modulator according to claim 14, wherein the absorbing element (94 in FIG. 6) is attached to the mirror (42).   15. The light modulator according to claim 14, wherein the absorbing element (94 in FIGS. 7 and 8) is attached to a ridge (100) extending in the gap (90). vessel.   An illumination system of a microlithography projection exposure apparatus comprising the light modulator according to any one of claims 9 to 16.

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